Square Miles to Hectares
Convert square miles to hectares instantly. 1 mi² = 258.9988110336 ha. Includes the exact factor, a conversion table of common values and the definition of both units.
How to convert square miles to hectares
To convert square miles to hectares, multiply by 258.9988110336. The relationship is fixed, so the same factor works for any quantity — there is nothing to look up and nothing that changes with temperature, location or context.
ha = mi² × 258.9988110336
Square Miles to Hectares conversion table
The values people look up most often, rounded for reading. Use the calculator above for anything in between.
| Square Miles | Hectares |
|---|---|
| 1 mi² | 258.998811 ha |
| 2 mi² | 517.997622 ha |
| 3 mi² | 776.996433 ha |
| 5 mi² | 1,294.99 ha |
| 10 mi² | 2,589.99 ha |
| 20 mi² | 5,179.98 ha |
| 25 mi² | 6,474.97 ha |
| 50 mi² | 12,949.94 ha |
| 100 mi² | 25,899.88 ha |
| 500 mi² | 129,499.41 ha |
| 1,000 mi² | 258,998.81 ha |
What is a square mile?
640 acres. Used for counties, states and weather-warning areas.
What is a hectare?
10,000 square metres, or about 2.471 acres. The global standard for farmland.
The formula
ha = mi² × 258.9988110336
Every result on this page comes from this formula. Nothing is rounded until the final display, so figures match a spreadsheet to the cent.
How to use the Square Miles to Hectares
- Type the number of square miles you want to convert.
- Read the result in hectares straight away — there is no button to press.
- Check the table below for the values that come up most often, or reverse the conversion with the linked hectares to square miles page.
Square Miles to Hectares — frequently asked questions
How many hectares are in a square mile?
One square mile equals 258.9988110336 ha. ha = mi² × 258.9988110336
What is the formula to convert square miles to hectares?
The formula is ha = mi² × 258.9988110336. It is an exact definition rather than an approximation, so the conversion never drifts no matter how large the number.
How do I convert hectares back to square miles?
Divide instead of multiplying: one hectare is 0.0038610216 mi². The reverse converter is linked in the related tools list.
Is this conversion exact?
Yes. Both units are defined against the same base unit by international agreement, so the factor is exact — any rounding you see is only in the display, which you can widen by entering more decimal places.
Is this square miles to hectares free to use?
Yes. Every calculator on the site is free, needs no sign-up, and runs entirely in your browser, so your figures never leave your device.
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About this calculator
Written and reviewed by The Samsung Calculator editorial team. Every calculator is written against a published formula, reviewed against at least one independent reference implementation, and dated when it changes.
Last reviewed August 15, 2026 · Calculation runs client-side · No data collected · Report an error